OFFSET
0,4
LINKS
E. de Panafieu and S. Dovgal, Symbolic method and directed graph enumeration, arXiv:1903.09454 [math.CO], 2019.
FORMULA
Sum_{n>=1} Sum_{k=1..n} T(n,k)*y^k*x^n/(n!*2^binomial(n,2)) = 1/(E(x) @ exp(- (x + s(x,y)))) where E(x) = Sum_{n>=0} x^n/(n!*2^binomial(n,2)) and @ is the exponential Hadamard product (see Panafieu and Dovgal) and s(x,y) is the e.g.f. for A367948.
EXAMPLE
Triangle begins ...
1;
1, 1;
3, 9, 4;
25, 277, 162, 48;
543, 38409, 18136, 6912, 1536;
29281, 23169481, 7195590, 2346000, 691200, 122880;
...
MATHEMATICA
nn = 5; B[n_] := n! 2^Binomial[n, 2]; s[x_, y_] := y x + (3 y + y^2) x^2/2! + (139 y + 3 y^2 + 2 y^3) x^3/3! + (25575 y + 103 y^2 + 12 y^3 + 6 y^4) x^4/
4! + (18077431 y + 4815 y^2 + 230 y^3 + 60 y^4 + 24 y^5) x^5/5! ;
ggf[egf_] := Normal[Series[egf, {x, 0, nn}]] /.Table[x^i -> x^i/2^Binomial[i, 2], {i, 0, nn}]; Map[Select[#, # > 0 &] &, Table[B[n], {n, 0, nn}] CoefficientList[Series[1/ggf[Exp[-(x + s[x, y])]], {x, 0, nn}], {x, y}]]
CROSSREFS
KEYWORD
AUTHOR
Geoffrey Critzer, Feb 19 2024
STATUS
approved